Railway track circuit apparatus



Feb. 10, 1942. PQH. CRAGO RAILWAY TRACK CIRCUIT APPARATUS I Filed June 22, 1940 I. a 0 H mw m m .m a M m w 2 i w W A a c I m\( v. a M A 0 1 z W Y A: B H 2 1 v JF L: 4 m

Patented Feb. 10, 1942 2,272,792 WAY TRACK CIRCUIT APPARATUS Paul H. Crago, Wilkinsburg, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application June 22, 1940, Serial No. 341,955 2 Claims. (Cl. 246-130) My invention relates to track circuit appa-' ratus; and it has particular reference to the organization of such apparatus into railway track circuits of the open circuit class wherein the winding of a track relay and a source of track circuit current are connected in series across the rails of a section of track in such manner that a circuit eiiective topick up the track relay is completed when and only when the wheels and axles of a train in the section establish a low resistance path across the track rails.

It has been proposed heretofore to utilize track circuits of the open circuit type to indicate traffic conditions in sidings, spurs, and other stretches of track where it is difiicult or impracticable to obtain the proper high resistance rail ballast conditions such as are required for economical operation of a track relay connected to the rails in the usual closed circuit arrangement. By using a track relay connected in an open circuit arrangement wherein the track relay and the track ballast resistance are connected in series, the current that is supplied to the track circuit when the section is unoccupied is limited by the two resistances in series and hence it is materially less than the current that is required for operation of a track circuit organized on the closed circuit principle wherein the track relay and the track ballast resistance are in multiple. A track circuit of the open circuit type accordingly is effective to conserve battery energy by avoiding excessive current consumption such as might occur if a stretch of track of relatively poor ballast resistance conditions were provided with a track circuit of the closed circuit type.

The parts of the apparatus incorporated into a track circuit organized on the open circuit principle must, of course, be arranged and proportioned so that when a train in the circuit establishes a low resistance rail-to-rail path, the current caused to flow in the circuit is sufficient to create in the track relay the energy level required to pick up the relay. This pick-up energy level of the relay is considerably higher than that required to hold the relay armature attracted once the relay picks up, with the result that the energy level normally available in the circuit after the train vacates the section to remove the low resistance rail-to-rail path, might cause the track relay under certain ballast conditions to be held up due to the current leaking across the ballast reaching a value sufficient to maintain the relay energized above its drop-away energy level. y

In View of the above mentioned and other important considerations, it is an object of my present invention to provide a track circuit of the open circuit class incorporating means efiective after a train in the section establishes a low re-:

sistance rail-to-rail path and the current flow.

in the track circuit reaches a value sufiicient to cause the track relay to pick up, to reduce the energy level in the track relay to a value only slightly above its drop-away energy level, whereby to avoid the possibility of falsely maintaining the relay energized after the train vacates the section.

Another object of my invention is .to incorporate into an open circuit class track circuit an auxiliary relay controlled by the track relay and in turn controlling theenergy levelof the circuit.

- A further object of my invention is to control the current supplied to a track circuit provided for a siding or spur track, by means of another track relay incorporated into a track circuit provided for an adjacent track and controlled by the track relay of the siding track.

A still further'object of my invention is the organization of track circuit apparatus into novel and improved arrangements for controlling highway crossing signals.

An additional object of my invention is to provide a novel and improved railway track circuit.

The above mentioned and other important objects and characteristic feature of my invention which will become readily apparent from the following description, are attained in accordance with my invention by employing a track relay and a source of track circuit current connected in series with the two rails of an insulated section of railway track in an open circuit arrangement such that a sufficient rail voltage normally is available to enable a train in the section to cause the track relay to pick up, and by employing means effective after the track relay picks up to reduce the current in the track circuit to a value only slightly in excess of that required to hold the relay energized. I prefer to effect the control of the current in the track circuit by means of an impedance which is rendered'ineffective to limit the current when the track relay is released, but which impedance becomes effective to limit or reduce the current after the track relay picks up. In accordance with my invention, an auxiliary relay controlled by the track relay is employed to control the efiectiveness of the impedance, and I prefer to employ as such auxiliary relay another track relay connected over a contact of the-first track relay in a track circuit of the normally closed cirmain track, and the other track Y, I shall term a siding or spur track. As shown, both tracks X and Y are intersected at grade by a highway H, and I shall assume that the distance between tracks X and Y along highway H is such that traflic on the highway may be protected ade quately by a warning device or devices common to both tracks X and Y, that is, the warning der vices are controlled by railway traffic on either track. Such warning devices may take any one of many suitable and well-known forms, and I have represented the intersection of highway H with tracks X and Y as being provided with one such device, designated by the reference character S and comprising an audible signal in the form of an electric bell.

The track rails I and Ia of trackY are divided by means of the usual insulated rail joints 2 into an insulated track section JK, which section includes the intersection of highway H with track Y. One terminal of a suitable source of track circuit current, such as a battery 3, is connected through the usual current limiting resistor 4 to rail I of section JK, and the other terminal of battery 3 is connected through the winding of a track relay TR and another resistor 5 to track rail Ia of section JK. As is readily apparent from an inspection of the drawing, the circuit connections of track circuit source 3 and track relay TR to the rails of section JK are such that the track circuit normally is open circuited and hence relay TR is normally deenergized.

The rails I and la of track X are divided by insulated joints 2 into two sections D-E and E-F, which sections extend in opposite directions from highway H. Sections D-E and E--F are each provided with a track circuit of the closed circuit class, and each track circuit comprises a track circuit current source I I connected across the rails at one end of the section and the winding of a track relay connected to the track rails at the opposite end of the section. As shown, the track relays of sections D-E and E-F comprise windings WI and W2, respectively, of an interlocking relay XR, and each winding of the interlocking relay is connected to the rails of its associated section over back contact 6 or back contact I, as the case may be, of track relay TR.

Relay XR may take any one of many wellknown forms of relays provided with an interlocking mechanism controlled by the armatures of windings WI and W2 and in turn controlling such armatures in such manner that the armature of the first winding to be deenergized is permitted to drop to its full-down position, and the movement of this armature actuates the interlocking mechanism to condition the mechanism to engage the armature of the other winding in the event such other winding becomes deenergized while the first winding is still deenergized. When an armature of winding WI or W2 is engaged by the interlocking mechanism,

it is permitted to drop only to an intermediate or interlocked position. The windings WI and W2 each control front and back contacts in such manner that when either winding is deenergized and its armature drops either to its full-down or to its interlocked position, its front contacts are opened, but such winding is permitted to close its back contacts only when its armature reaches its full-down position. In accordance with the usual construction, the arrangement of the interlocking mechanism of relay XR preferably is "such that when both windings WI and W2 are simultaneously deenergized, the armatures of both windings drop to their full-down positions and neither armature is retained by the interlocking mechanism in an interlocked position.

Windings WI and W2 of relay XR control, over back contactsld and I5, respectively, an obvious operating circuit for signal S extending from one terminal B of a suitable source of current, such as a battery not shown, through back contact. I4 or I5 of relay XR and the winding of signal S to the other terminal C of the source of current; and such windings also control at front contacts 8 and 9, respectively, a shunt circuit around resistor 5 interposed between one terminal of relay TR and rail Ia of section JK.

When both tracks X and Y are unoccupied, relay TR. is released to close its back contacts 6 and I and thus complete the circuit for windings WI and W2, respectively; windings WI and W2 are energized and close front contact 8 and front contact 9, respectively, to shunt resistor 5 interposed between relay TR and rail Ia of track Y; and signal S is deenergized.

The parts of the apparatus incorporated into the track circuit of section JK are so arranged and proportioned that under the above assumed normal conditions, the energy level created in relay TR by the current normally flowing in the track circuit is insumcient to pick up the relay. When, however, a train enters section J-K and establishes a low resistance path from one rail to the other, relay TR becomes effectively energized and picks up due to the increased current caused to flow in the track circuit of section J-K in response to the low resistance railto-rail path established by the train. Relay TB in picking up opens its back contacts 6 and I to thereby open simultaneously the previously mentioned circuits of windings WI and W2, and the armatures of both windings of relay XR thereupon drop to their full released positions to close back contacts I4 and I5 and thus complete the obvious operating circuit for signal S.

The releasing of windings WI and W2 also causes their front contacts 8 and 9 to become opened to open the shunt path around resistor 5, which accordingly becomes effective to limit the current supplied to relay TR. to a value only slightly in excess of that required to maintain the relay above its drop-away energy level when the train in the section establishes its low resistance path from one rail to the other. It follows, therefore, that when the train vacates the section to remove the low resistance connection between the rails, relay TR quickly releases. When relay TR releases, its back contacts 6 and I become closed and windings WI and W2 become reenergized to terminate operation of signal S and to again shunt resistor 5 interposed between relay TR and rail Ia of section JK.

The operation of windings WI and W2 for a train operating on track X is believed to be obvious, and further description of the operation of such apparatus accordingly is deemed unnecessary.

From the foregoing description, it can be seen that I have provided a track circuit arranged on the open circuit principle, wherein the energy normally available to assist a train in the section to establish a low resistance path between the track rails and thus complete the circuit of the relay, is reduced after the track relay picks up to avoid the possibility of maintaining the track relay energized by excessive current leakage across the track ballast such as might be caused if the normal energy level were available when the section becomes vacated.

It is, of course, to be understood that although signal S has been illustrated as governed by contacts of the auxiliary relay XR controlled by relay TR, such signal might if desired be controlled directly by contacts of relay TR. Also, it is to be understood thatwhile I haveherein shown and described my invention in connection with a highway crossing signal system wherein relay TR connected in the open circuit track circuit controls both windings of an interlocking relay which functions as an auxiliary relay for relay TR, my invention is in no way limited in use to the particular embodiment shown, but it may be employed wherever it' is desired to improve the operation of a track relay connected in an open circuit track circuit.

It should, however, be noted that by utilizing a track relay of an adjacent stretch of track as an auxiliary relay for relay TR, no additional relays are required to effect my invention and the additional apparatus required is extremely simple and economical inasmuch as it consists only of circuit wires and an extra resistor.

Although I have herein shown and described only one form of railway track circuit apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, two adjacent stretches of railway track, two insulated sections one for each track, a source of track circuit current and a track relay connected in series across the rails of one of said sections, another source of current connected to the rails of the other of said sections, another track relay connected over a normally closed contact of said first track relay to the rails of said other section, and means controlled by said other track relay when released for reducing the current supplied from said first source to the rails of said first section.

2. In combination with two adjacent stretches of railway track both intersected at grade by a highway, a highway crossing signal located at such intersection for protecting highway traffic over both of said tracks, two insulated sections one for each track and each extending into the intersection, a first source of current and a first track relay connected in series across the rails of a first of said sections, a second source of current connected to the rails at one end of the second of said two sections, a second track relay connected over a normally closed contact controlled by said first track relay to the rails at the other end of said second section, means controlled by said second relay for operating said signal, and means also controlled by said second relay for limiting the current supplied from said first source to the rails of said first section.

PAUL H. CRAGO. 

